I used to edit PDFs using GIMP. I would open the PDF in GIMP, make edits, export it as a .mng file, and convert it back.

$ convert -reverse pdf.mng pdf.pdf

This would work well except all the texts were rasterized.

I recently tried editing PDFs using LibreOffice Draw again and was delighted to discover its PDF editing capabilities have improved. Gonna use LibreOffice Draw from now on.